Uptake of Heavy Water and Loss by Tangerine in the Heavy Water Vapor Release Experiment in a Greenhouse as a Substitute for Tritiated Water

Heavy water (D₂O) vapor release experiments were carried out in a greenhouse using deuterium as a substitute for tritium and uptake and loss kinetics of D₂O in leaf of a tangerine tree and formation, translocation and retention of organically bound deuterium (OBD) in tangerine exposed to D₂O under different growth stage were investigated. Rate constants of D₂O uptake in leaves of tangerine were 0.2-1.11 hr^-1 in the daytime release and 0.03-0.12 hr^-1 in the nighttime release. Rate constants of D₂O loss in leaf after daytime release were almost the same as those after the nighttime release. No significant differences in the half time of D₂O loss were observed between daytime and nighttime releases, but those in winter experiments were about 6 times higher than those in summer ones. The retention of OBD of the edible part of tangerine at harvest was very low and OBD was 0.08% or 0.07% on average of D₂O in air moisture in daytime or nighttime releases.